Pressure sensors and methods of manufacturing pressure sensors are known. In the U.S. Pat. No. 7,704,774 B2 for example, there is described a pressure sensor, which is manufactured by joining two substrates, the first substrate comprising CMOS circuitry and the second being an SOI substrate. A cavity is formed in a top material layer of the first substrate, which is covered by the silicon layer of the second substrate. Part or all of the substrate of the second wafer is removed to form a membrane from the silicon layer. Alternatively it is further described that the cavity can be formed in the second substrate. The second substrate is electrically connected to the circuitry on the first substrate. The known design allows for the use of standard CMOS processes for integrating circuitry on the first substrate.
In pressure sensors the membrane may be sensitive to stress. When a pressure sensor is mounted with its back side to a carrier and is electrically connected thereto mechanical stress may be evoked and transmitted via solder balls to the first substrate and specifically to stress sensitive structures of the pressure sensor such as the membrane.